The invention provides a contra-angle ultrasonic endodontic instrument.
In providing endodontic therapy, it is important for the dentist to completely clean all organic matter from the root canal of the tooth prior to filling it with medication or other material, otherwise inflammation and infection may result requiring the treatment to be repeated or the tooth to be removed. A typical theraputic approach followed at present requires the dentist to insert a narrow diameter file into the root canal sufficiently to reach the apex of the tooth, as measured on an X-ray, then to clean the root canal using this file and progressively larger files until only clean white dentin shavings are extracted with an irrigating solution. Since no satisfactory instrument at present exists to permit a dentist to perform endodontic operations on molars, in part because of their location and in part because of the complex shape of their root canals, for the most part such treatments are performed by hand. As a result, they are tiring, can prove quite difficult, and often result in incomplete or uneven removal of the nerve and pulp material, and bacteria. It would be most helpful to have an endodontic instrument capable of performing such treatments, particularly on molars for not only would such an instrument prove to be less tiring to the dentist but it also likely would result in improved cleansing of the root canal and therefore minimize inflamation and infection.
Various endodontic instruments have been designed; some of them have been patented. A recent endodontic instrument which is ultrasonically driven is being marketed by Cavitron, Inc. of Long Island City, N.Y. It is known as their Cavitron Ultrasonic Unit 1010 with a PR-30 ultrasonic insert. This insert includes, in addition to the ultrasonic driver, a shaft which transmits the ultrasonic vibrations through a block to an ultrasonic tool, the longitudinal axis of the tool being parallel to the longitudinal axis of the shaft. As a result, while this tool could be quite useful for performing endodontic treatments in teeth at the front of the patient's mouth, it is of limited usefulness for performing such treatments in molars. It would be highly desirable if the longitudinal axis of the endodontic tool were turned to lie at a substantial angle to the longitudinal axis of the shaft and instrument, and arrangement commonly termed a "contra-angle" instrument. It would also be highly desirable if such an instrument could be used in root canals of complex shapes.
The usefulness on a contra-angle instrument is well known; many such instruments have been designed and are in current use by dentists. Ultrasonic instruments also are well known. In view of these facts, it would seem to be a simple matter to provide a contra-angle, ultrasonic instrument for endodontic applications. While this objective certainly might be readily apparent to the designers of dental instruments, so far as is known, prior to this invention no such instrument has proven successfully for such application. The problem is a simple one. It is essential that the endodontic tool not break while in the root canal of a tooth. If it does, the dentist must spend a great deal of time trying to dislodge and work loose the broken tip. Often this effort is unsuccessful. At times, though, it is not. Ultrasonic instruments such as the Cavitron Ultrasonic Unit 1010 with the PR-30 insert are designed to transmit the major ultrasonic vibrations longitudinally through the shaft of the endodontic tool. As a result, when used in root canals of complex shape, they do not appear to produce, or result in, more than a normal number of tip breakage occurances during endodontic treatments. However, if the instrument is designed or modified so that the longitudinal axis of the endodontic tool lies at a substantial angle to the longitudinal axis of the shaft of the instrument, or if it is used in a root canal of complex shape, the ultrasonic vibrations apparently are transmitted with substantial transverse components to the endodontic tool. These transverse components appear to induce appreciable breakage of the tool resulting in a highly unsatisfactory instrument-at least that has been the experience of those instrument designers known to the present inventor. As a result, efforts to provide a contra-angle ultra sonic endodontic instrument largely have been abondoned in spite of the considerable appeal such as instrument would offer for endodontic work.
To understand the present invention, it is also important to know something about the various lines of endodontic tools. There are basically three types: broaches, reamers and files. All are tapered from a relatively large diameter base to a small diameter tip. A broach is a barbed tool; it has a number of leaves or barbs carved out of its sides which, upon drawing the tool out of the root canal, carve a portion out of the side of the canal. A Hedstrom file looks from the side like a number of cones with the apex of each stuck to the base of the next. Thus, neither a broach nor a Hedstrom file has a relatively uniform longitudinal and lateral cross-section. Both include areas or indentations laterally which substantially weaken the shaft. If lateral ultrasonic vibrations are transmitted to such shafts, they tend to break at such weakened areas. The reamer or file, however, is of relatively uniform longitudinal and lateral cross-section that is spiraled longitudinally. Some are of triangular cross-section; others have a square cross-section. Since they do not include laterally weakened areas, it has been found that ultrasonic vibrations with substantial lateral components can be imposed upon such endodontic reamers without tending to break them. Indeed, it has been found that such a reamer or file can be inserted into the complex, curved root canal of a molar, ultrasonic vibrations imparted to it with substantial lateral components, and the reamer or file used to perform endodontic treatments without experiencing any unusual number of tip breakages. Further, it has been found that should a tip break, another tool can be inserted into the root canal and its ultrasonic vibrations imparted to the broken tip through an irrigant or other fluid to quickly and easily float it free.
The present invention is based upon this important, new discovery.